Port statisticsproxymodel away from QApplication

Carl Schwanrequested to merge
work/carl/statisticsproxymodel-widgets-free into master

The QPalette usage is useless as the tooltip will use by default the QPalette colors and the layout direction can be extracted from the QGuiApplication.

Fix also a QString::arg call with the wrong replacement number.

Tested with a white and dark theme

Edited by Carl Schwan

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